<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title>第52个CSS页面</title>
</head>
<body>
<p>参与折叠的外边距既有正值又有负值</p>

<div style="height: 50px; margin-bottom: -50px; width: 50px; background-color: red;">A</div>
<div style="height: 50px; margin-top: 100px; width: 50px; background-color: green;">B</div>
</body>
</html>